Table 2 - Fastener Sizes
The ANSI preferred metric sizes are identical to those in the ISO 497 R20'' rounded series selected years ago. The intent of the number series shown is to help reduce the number of standard sizes for screw threads, metal sheets and plates, round metal bars, lifting capacities, hydraulic cylinder diameters, etc.
The preferred size range from 4 through 40 mm may be extended to cover smaller or larger sizes by just multiplying or dividing sizes shown by 10. For instance, 60-mm sizes would be a preferred choice as would 2.5-mm devices.
For example, the six first choice thread sizes shown in TABLE 2 are recommended to replace the 61 other thread sizes listed. The first choice sizes are according to the R5" series of preferred sizes shown in TABLE 1. Less savings will be achieved if you select the twelve ISO (green) first and second choice sizes shown or the 14 ANSI (bold) first choice sizes. The cost reduction becomes substantial when you figure thousands of dollars savings for each unique fastener size that can be eliminated from the product design.